Air flow meter NISSAN 300ZX 1984 Z31 Engine Fuel And Emission Control System Workshop Manual

PRECAUTIONS
Always use 12 volt batteries as * Do not disassemble E C C S When installing large capacity wire-
Do not attempt to disconnect Do not turn diagnosis mode sure to obsetve the following as it power source
battery cables while engine
IS
control unit
selector less equipment or a vehicle phone, be
may adversely affect electronic con-

operating
Do not apply battery power
directly to injectors
Do not remove the fuel tem-
perature sensor from
the T

pressure regulator
Replace as an assembly
trol systems depending on its installa-
tion location
1) Keep the antenna as far as possible
away from the electronic control
units
2) Also keep the antenna feeder line
more than
20 cm (7 9 in) away from
the harness of electronic controls
Do not let them run parallel for a
long distance
3) Adjust the antenna and feeder line so
that the standing-wave ratio can be
keot smaller
J
Handle air flow meter care-
fully to avoid damage * Do not disassemble auxiliary
Do not disassemble air flow air control valve (VG30ET
meter engine)
Do not clean air flow meter
with any type of detergent
0 Even a slight leak in the air in- /
&&%$$?&
take system can cause serious
problems
Do not depress accelerator Do not shock or jar the crank
angle sensor
Immediately after starting, do
pedal when starting
not rev
up engine unneces-
sarily
Do not rev up engine just prioi
to shutdown
Do not operate fuel pump when
there is no fuel in lines Do not use anti-freeze agents in fuel
0 Do not reuse fuel hose clamps
0 Tighten fuel hose clamps sufficiently
Securely connect E C C S harness
connectors
A poor connection can cause an ex-
tremely
high (surge) voltage to
develop in coil and condenser, thus
resulting in damage to IC circuit
Keep
E C C S harness at least 10 cm
(3 9 in) away from adjacent
harnesses, to prevent an
E C C S
system malfunction due to reception
of external noise, degraded operation
of
IC circuit. etc
Keep E C C S parts and harnesses
Before removing parts, turn off igni-
tion switch and then disconnect
battery ground cable dry
SEF6008
EF & EC-2

E. C. C.S. CHART
VG30ET Engine (With turbocharger)
Air flow meter c
Cylinder head temperature sensor b
b
Ignition switch b
Throttle valve switch I b
b
Park/Neutral switch
Air conditioner switch I
b
E C C.S
control
unit
b
Injectors Fuel injection &
mixture ratio control
--I
Ignition timing control Power transistor
-dI Auxiliary air control
(A A
C ) valve Idle speed control
I YL
E G R control E G R control solenoid valve
Fuel pump control Fuel pump
Inspection lamps ixhaust gas sensor
nonitor
& self diagnosis I
EF & EC-7

AIR FLOW SYSTEM DESCRIPTION
TURBOCHARGER
The turbocharger is installed on the exhaust mani-
fold This system utilizes exhaust gas energy to
spin the turbine wheel which
is directly connected
to the compressor wheel The compressor supplies
pressurized air through the throttle chamber into
the intake manifold Thus, the turbocharger in-
creases charging efficiency and thereby increases
power and torque.
To prevent an excessive rise in the supercharging
pressure, the turbine speed
is maintained within a
safe range by controlling the amount of exhaust
gas that passes through the turbine This system
consists of
a by-pass valve which allows some of
the exhaust gas to by-pass the turbine and to flow
directly into the exhaust tube
Engine speed
From b==iF exhausi man2fold 0 Superchargang pressure 41 hqh
To intake
From air flo meter
h
To intake
From air flo meter
2 Bygars valve controller
3 Compressor
4 Turbine
SEF609B
EMERGENCY RELIEF VALVE
To prevent an abnormal rise in supercharging
pressure, and possible engine damage, in case
the
by-pass valve fails to open properly, an emergency
relief valve
is provided as a safety device on the
intake manifold
When the prwre in the Intake mandold IS below 52 0 kPa 1390 mmHg. 15 35 inHgl
Upper cover
When the prerrura tn the intake mandold IS above 520 kPa 1390 mrnHg, 15 35 mHg)
Atmosphere
Charged air pressure Charged air pressure
SEF6lOB
EF & EC-12

E.C.C.S. DESCRIPTION
E.C.C.S. Components (Cont'd)
A
Air flow meter 0.
C
AIR FLOW METER
The air flow meter measures the mass flowrate of
intake air. Measurements are made in such
a man-
ner
that the control circuit emits an electrical out-
put signal
in relation to the amount of heat dissi-
pated from the hot wire placed
in the stream of
intake
air.
E F I relay
Battery source
Output voltage
Variable resistor
25 unit Ground
Self-cleaning ignition switch
Ground
El -
-
6- 31 27 35 1
w30 ECCS 6 comroi
F- 12 34 -
-
I SEF615B
SEFSlSB
The air flowing around the hot wire removes the
heat from
the hot wire The temperature of the hot
wire
is very sensitive to the mass flowrate of the
air.
The higher the temperature of the hot wire, the
higher
its resistance value This change in the
temperature (or. resistance)
IS determined by the
mass flowrate of the air. The control circuit
ac-
curately regulates current (I) in relation to the
varying resistance value
(RH) so that VA always
equals VB The air flow meter transmits an output
for voltage
VA to the control unit where the
output
is convened into an intake air signal.
I
Temperature compensation resistor
twire
Hot wore reststance
Temperature campenration resistance RA. RB Constant reSiiIanCe
RH RK
SEFS17B
I
EF & EC-14

E.C.C.S. DESCRIPTION
Fuel Injection Control
Temperature of engine Cylinder head temperature sensor
Density of oxygen in exhaust gas Exhaust gas sensor
Throttle valve idle position ' Throttle valve switch
Engine speed and piston position
Amount of intake air Air flow meter
ECCS
I I
I
control
Gear position unit NeutraVPark switch (VG30ET) I I
Vehicle speed
Start signal
Temperature of fuel
Battery voltage Battery
The E.C C S control unit calculates basic injection
pulse
width by processing signals from crank angle
sensor and air flow meter Receiving signals from
each sensor which detects various engine condi-
tions,
E C.C S control unit adds various enrich-
ments, which are pre-programmed
in the control
unit, to the basic injection amount. Thus, the op-
timum amount of fuel is injected through the
injectors.
1 ) Fuel enrichment
In the following each conditions, fuel is
enriched
e During warm-up
When starting
After idle
e When accelerating
e With heavy load
e When fuel temperature is high
.I Injector
Rlch
' \/ .-Warm-u~ enrichment
Cylmder head temperature (or fuel temperature1 SE F637 0
Enrichment rates for "when accelerating" and
"with heavy load" are pre-programmed for engine
speed and basic injection pulse
width
EF & EC-20

E. C. C. S. DESCRIPTION
Ignition Timing Control
Engine speed and piston position Crank angle sensor
Amount of intake air Air flow meter
Temperature of engine Cylinder head temperature sensor
Throttle valve idle position
Vehicle speed Vehicle speed sensor (VG30ETl 1 I I
Start signal Ignition switch
Engine knocking Detonation sensor
Battery voltage Battery ~
Ignition
timing is controlled, corresponding to the
engine operating conditions, by the
E C C S con-
trol unit that
is, as the optimum ignition timing in
each driving condition has been pre-programmed in
the control unit, the ignition timing
IS determined
by electrical signals processed in the unit
The signal from
E C C S control unit is trans-
mitted to power transistor, and controls ignition
timing
The retard system by detonation sensor
is designed
only for emergencies on VG30ET engines. The
basic ignition timing
is pre-programmed within the
anti-knocking zone, even
if recommended fuel is
used under dry conditions Consequently, the
retard system does not operate under normal
driving conditions
However,
if there engine knocking occurs, the
detonation sensor monitors knocking condition
and the signal is transmitted to the E.C.C S
control unit After receiving it, the control unit
retards the ignition timing to avoid the knocking
condition
Power transistor
EF & EC-23

DIAGNOSTIC PROCEDURE
b NG 3 Check idle speed and ignition timing
Driveability
(--- START -l
Adjust to specifications
4 Check mixture ratio feedback system Clean injectors or adjust to specifications
I 5 Perform driveability test I
OK NG
Repair or replace components as necessary
P
6 Perform electronic control system inspection
OK I
Adjust to specifications
OK 1 I
NG 4-
7 Check idle mixture ratio
, I
I
Replace air flow meter. 8 Check mixture ratio at middle engine NG
speed
OK
) 9 Perform driveability test
EF & EC-29

DIAGNOSTIC PROCEDURE
Driveability (Cont'd)
7) If N G., adjust idle mixture ratio by turning
variable resistor on
air flow meter so that
inspection lamps blink simultaneously
SEF649B
B Check mixture ratio at middle engine speed
1) Verify that inspection lamps on control unit
blink simultaneously at idle.
2) Race engine two or three times under no-load,
then run engine
at idle speed
3) Gradually increase engine speed and check for
operating (blinking)
of the inspection lamps at
different engine rpms (up to approximately
2,000 rprn).
If both inspection lamps continue to blink
during idle to
2,000 rpm range, it indicates that
the idle mixture ratio is correct
4) If N.G., replace air flow meter and adjust idle
mixture ratio
as per step 7
5) Turn off engine and connect throttle valve
switch harness connector
9. Perform driveability test
Reevaluate vehicle performance.
EF %t EC-32

SELF-DIAGNOSIS
Self-diagni
The self-diagnostic system determines malfunctions
of signal systems such as sensors, actuators, and
wire harnesses based on the status of the input
signals received by the
E C C S control unit
A malfunction is displayed by both the red and
green
L E D s (Light Emitting Diodes).
Basically, self-diagnosis
is always performed when
the power
is furnished to the E C C S control
unit The self-diagnosis results
are retained in the
memory chip of the
E C C S control unit and are
displayed only when the diagnosis mode selector
(located on
the side of the E C C S. control unit) is
turned fully clockwise
The self-diagnostic system
is provided with func-
tions which display malfunctions being checked
as well as those which are stored in the memory
In
this sense, it is very effective in determing an
"intermittent" malfunction The results which
is
or was stored in the memory can be erased by
following the steps specified
A malfunctioning area is determined by the num-
ber of blinks of both the
red and green L E D s
First, the red L E D blinks and the green follows
The red L E D refers to the tenth digit while the
green
one refers to the unit digit. For example,
when the red L
E D. blinks three times and the
green
L E.D blinks twice, this implies number
"32" In this way, all problems are classified by
code numbers.
inspection lamps1 Diagnosis mode
SEF6508
Judging the selfdiagnosis results
1 When the ignition switch is turned "ON",
the diagnostic system judges
a malfunction
tic System
until the specified input signal is entered and
detected
as 0 K
(These input signals are not stored in the
memory
)
1) Vehicle speed sensor circuit (VG30ET engine)
When the vehicle speed exceeds
10 km/h
(6 MPH) and its corresponding signal is entered
2) Throttle valve switch (idle switch) circuit,
neutral switch circuit (VG30ET engine) and
air
conditioner switch circuit
After the ignition switch
is turned "ON" and
"ON-OFF"
signals from each switch are
entered
3) Start signal
After the engine has started and when start
signals "ON" and then "OFF" are entered
2 After the self-diagnostic system has detected
a malfunction, it continues to provide a mal-
function display until the memory
is erased
properly by the sepcified steps
1) Crank angle sensor circuit
When 1" or 120" signal is not entered after
the engine has started
When either 1" or 120" signal is not entered
often enough
2) Air flow meter circuit
When the air flow meter produces an abnormal-
ly high output voltage with the engine off
When the air flow meter produces an abnormal-
ly low output voltage with the engine running.
3) Cylinder head temperature sensor circuit
When the cricuit
is shorted or open
4) Ignition signal
When an ignition signal
is not produced on the
primary winding of the ignition coil after
the
engine has started
5) Fuel pump circuit
When current flowing through the E
C C.S
control
unit to drive the fuel pump IS too
small or too large while the engine
is operating.
6) Detonation sensor circuit (VG30ET engine)
When the circuit
is shorted with the engine
operating
at a speed of above 2,000 rpms
When the circuit is shorted or open
7) Fuel temperature sensor circuit
EF & EC-35

SELF-DIAGNOSIS
Decoding Chart
I Code No 11
I ked Green
00
1 CodeNo 12
I 'Red Green
0 00
Crank angle sensor circuit IS malfunctioning
Air flow meter circuit IS
malfunctioning 1
See page
EF & EC43
SEF6578
EF & EC44 & 45
1
SEF658B II
I CodeNo 13 I
Cylinder head temperature sensor clrcuit IS malfunctioning
See page EF & EC-46
SEF659B II
Vehtcle speed sensor circuit IS malfunctioning (VG30ET engine)
See page
EF & EC47
Id SEF660B
EF & EC-39